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Unit  3:  Physiological  Systems  

Nervous  System  Endocrine  System  

ReproducAve  System  CELLS  TISSUES  ORGANS  

ORGANISMS  POPULTIONS  COMMUNITIES  

ECOSYSTEMS  

Cellular  communicaAon  

CELLS  TISSUES  ORGANS  

ORGANISMS  POPULTIONS  COMMUNITIES  

ECOSYSTEMS  Each  step  requires  communicaAon  and/or  interacAon  

Cellular  communicaAon  

CELLS  TISSUES  ORGANS  

ORGANISMS  POPULTIONS  COMMUNITIES  

ECOSYSTEMS  Ecosystems  WILL  NOT  funcAon  without  cell-‐cell  communicaAon!  

•  Cell-‐cell  communicaAon  is  one  of  the  most  important  evoluAonary  advancement  of  life.  

HOW  DOES  IT  HAPPEN?    

Cellular  communicaAon  

Signaling:  cells  “talking”  to  one  another  

Transmission:  How  the  signals  are  moved  or  passed  between  cells  

Control  systems  

NERVOUS  SYSTEM  •  Fine,  rapid  movements  – Muscle  control  

•  Neurons  •  Synapses  

ENDOCRINE  SYSTEM  •  Slow  movements,  wide  temporal  range  – Metabolic  processes  

•  Hormones  

•  Physiological  systems  that  detect  changes  and  respond  accordingly  

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Control  systems  

NERVOUS  SYSTEM  •  Fine,  rapid  movements  – Muscle  control  

•  Neurons  •  Synapses  

ENDOCRINE  SYSTEM  •  Slow  movements,  wide  temporal  range  – Metabolic  processes  

•  Hormones  

SENSORY  SYSTEM  •  How  body  receives/sends  sensory  signals  

Control  systems  

NERVOUS  SYSTEM  •  Fine,  rapid  movements  – Muscle  control  

•  Neurons  •  Synapses  

ENDOCRINE  SYSTEM  •  Slow  movements,  wide  temporal  range  – Metabolic  processes  

•  Hormones  

SENSORY  SYSTEM  •  How  body  receives/sends  sensory  signals  

•  Most  Assues  under  control  of  both  nervous  and  endocrine  systems  

Cell  Signaling  

1.  Ch.  11:  Neurons  –  Structure  –  CommunicaAon  •  AcAon  potenAals  

2.  Ch.  2:  Synapses  –  Structure  –  CommunicaAon  •  NeurotransmiWer  

Nervous  system:  Tissues  and  cells  

Nervous  system  

Neural  Assues  

Nerve  cells  (neurons)  

Glial  cells  

Neurons  •  Cell  that  is  adapted  to  generate  an  electrical  signal  – AcAon  potenAal:  a  short,  self-‐propagaAng  impulse  

•  Signals  from  other  cells  received  at  synapses  – Contact  points  between  cells  

Neuron  structure  •  4  main  parts:  1.  Dendrite  2.  Cell  body  (soma)  3.  Axon  4.  PresynapAc  terminal  

•  Label  these  4  parts  on  your  sheet    –  Include  funcAon  of  each  

 

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Neuron  structure  •  4  main  parts:  1.  Dendrite  –  Site  of  synapAc  

input  à  Receives  signals  from  other  neurons  

–  Conveys  informaAon  to  the  cell  body  

 

                                     

                                     

                                     

                                     

                                     

Neuron  structure  •  4  main  parts:  1.  Dendrite  2.  Cell  Body  (soma)  –  Signals  received  

and  impulses  generated  

                                     

                                     

                                     

Neuron  structure  •  4  main  parts:  1.  Dendrite  2.  Cell  Body  (soma)  3.  Axon  –  Carries  

informaAon  away  –  ConducAon  of  

impulse  via  acAon  potenAal  (AP)  

–  Axon  hillock:  Where  AP  starts  

                                     

                                     

Neuron  structure  •  4  main  parts:  1.  Dendrite  2.  Cell  Body  (soma)  3.  Axon  4.  PresynapAc  

terminals  –  Output  of  neuron    –  NeurotransmiWer  

secreted    

•  Cell  body  composed  of  normal  cell  organelles  

•  #  axons  and  dendrites/neuron  determines  the  type  and  funcAon  of  neuron  

Neuron  structure  •  Some  axons  covered  in  myelin  sheaths  –  Increase  speed  of  impulse    

– Physical  and  metabolic  support  for  neurons  

– Made  up  of  Glial  cells  

Neuron  structure  

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•  Glial  cells:  1.  Schwann  Cells  (PNS)  2.  Oligodendrocytes  

(CNS)  –  Insulate  and  

increase  impulse  transmission  velocity  along  axons  

Neuron  structure   Neuron  structure  •  Glial  cells:  1.  Schwann  Cells  (PNS)  2.  Oligodendrocytes  

(CNS)  3.  Astrocytes  •  Line  capillaries    •  Aid  communicaAon  

between  circulatory  and  nervous  systems  

Neuron  structure  •  Glial  cells:  1.  Schwann  Cells  (PNS)  2.  Oligodendrocytes  

(CNS)  3.  Astrocytes  4.  Microglial  cells  •  Mediate  immune  

system  response  •  May  consume  

pathogens  and  cellular  debris  caused  by  injury  

Neurons  •  Neurons  that  ‘end’  as  synapses  on  another  neurons  are  innervated  

•  All  neurons  connected  in  vast  web  à  Nervous  System  

Neuron  Structure  Video  

Chapters  11  and  12  

1.  Neurons  –  Structure  –  CommunicaEon  •  AcAon  potenAals  

2.  Synapses  –  Structure  –  CommunicaAon  •  NeurotransmiWer  

Neurons  generate  acAon  potenAals  

•  Neurons:  Cell  that  are  adapted  to  generate  an  electrical  signal  

•  AcAon  potenAal:  a  short,  self-‐propagaAng  impulse  – VERY  fast  (0.4-‐3  ms!)  

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AcAon  potenAals  

AcAon  PotenAal  Video  

Change  in  membrane  permeability  to  specific  ions  

Membrane  potenAal:  occurs  when  there  is  an  ion  concentraAon  gradient  across  membrane  

Change  in  membrane  potenAal  

ACTION  POTENTIAL    

•  VOLTAGE-‐DEPENDENT:  Caused  by  change  in  membrane  potenAal  (ion  concentraAon  gradient)  

•  VOLTAGE-‐DEPENDENT:  Caused  by  change  in  membrane  potenAal  (ion  concentraAon  gradient)  

•  ALL-‐OR-‐NONE:  only  occur  when  voltage  threshold  is  reached  

AcAon  potenAals  

AcAon  potenAals  •  Caused  by  increased  

ion  permeability    –  Na  and  K  

•  Four  phases:  1.  ResAng  membrane  

potenAal  (start)  2.  Rising  phase  3.  Falling  phase  4.  Recovery  

AP  Phases:  ResAng  membrane  potenAal  

•  K+  leak  channel  always  open  – K+  diffuses  in/out  in  small  amounts  according  to  electrochemical  gradient  

 

•  SAmulus  à  membrane  depolarized  above  threshold    – Voltage-‐gated  channels  open  à  more  permeable  to  Na+  

– Na+  rushes  into  cell  due  to  concentraAon  gradient  

AP  Phases:  Rising  Phase  

1.  Na+  channel  inacAvaAon:  decreased  permeability  to  Na+  

2.  Voltage-‐gated  K+  channels  open  –  K+  exit  cell  towards  equilibrium  

AP  Phases:  Falling  Phase  

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•  Voltage-‐gated  K+  channel  stays  open  briefly  •  Na+  channels  close  (no  ion  concentraAon  gradient)  

AP  Phases:  Recovery  

•  VOLTAGE-‐DEPENDENT:  Caused  by  change  in  membrane  potenAal  

•  ALL-‐OR-‐NONE:  only  occur  when  voltage  threshold  is  reached  

•  PROPAGATION:  UnidirecAonal  

AcAon  potenAals  

AcAon  PotenAal  Video  

and  FAST  

AP  propagaAon:  Velocity  1.  Greater  axon  

diameter  à  faster  impulse  

AP  propagaAon:  Velocity  1.  Greater  axon  

diameter  à  faster  impulse  

2.  More  insulaAng  myelin  (Schwann  cells  or  Oligodendrocytes)à  faster  impulse  – APs  only  occur  at  Nodes  of  Ranvier  

– APs  “jump”  past  myelinated  internodes  

AP  propagaAon:  Velocity  1.  Greater  axon  

diameter  à  faster  impulse  

2.  More  insulaAng  myelin  (Schwann  cells  or  Oligodendrocytes)à  faster  impulse  

More  myelin  

APs  can  travel  faster  travel  along  skinnier  axons  

Can  pack  more  axons  into  smaller  spaces  

More  complex  organisms  possible  

AP  propagaAon:  Velocity  1.  Greater  axon  

diameter  à  faster  impulse  

2.  More  insulaAon  (more  myelin)  à  faster  impulse  

3.  Higher  temperature  à  faster  

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3  types  of  neurons  1.  Spiking  

1.  SAmulus  triggers  acAon  potenAal  

2.  AP  travels  train-‐like  down  axon  •  Frequency  of  AP  

determines  amplitude  (strength)  

1.  Sensory  sAmulus  

2.    AcAon  potenAal  

3.    NeurotransmiWer  released  at  axon  

terminal  

4.  SynapAc  Input  

3  types  of  neurons  1.  Spiking  2.  Non-‐spiking  –  Impulse  spread  

electronically  (No  AP  generated)  

–  Short  neurons  •  Photoreceptors  •  ReAna  cells  •  Olefactory  cells  

3  types  of  neurons  1.  Spiking  2.  Non-‐spiking  3.  Spontaneous  –  Impulses  sent  at  

regular  intervals  without  sAmulus  •  Cardiac  Assues  •  Pacemaker  cells  

Chapters  11  and  12  

1.  Neurons  –  Structure  –  CommunicaAon  •  AcAon  potenAals  

2.   Synapses  –  Structure  –  CommunicaAon  •  NeurotransmiWers  

Synapses  •  Specialized  site  of  contact  between  two  neurons  or  between  effector-‐neuron  

•  SynapEc  cleI:  Any  space  between  neurons  

SynapAc  transmission  •  “CommunicaAon”  from  presynapAc  to  postsynapAc  cells  across  synapAc  clem  – Very  fast  

•  Electrical  or  chemical  

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SynapAc  transmission:  Electrical  •  Charge  moves  across  gap  juncAon  – Low-‐resistance  pathway  for  current  flow  across  protein  channels    

•  Connexons  •  PROBLEM:  Loss  of  amplitude!  

SynapAc  transmission:  Chemical  •  Slower  •  Excitatory:  raises  probability  of  cell  generaAng  

AP  or  increases  AP  frequency  •  Inhibitory:  lowers  probability  of  AP  or  

frequency  

SynapAc  transmission:  Chemical  •  Chemical  transmission  

involves  the  release  of  a  neurotransmi+er  –  1  neuron  produces  1  type  

of  neurotransmiWer  –  Receives  many  (may  be  

connected  to  >  1  synapse)  

•  Dozens  have  been  IDed  •  HUGE  diversity  in  funcAon  

Diversity  of  neurotransmiWers  

SynapAc  transmission:  Chemical  •  To  be  considered  a  neurotransmiWer,  a  chemical  

must:    1.  Be  present  in  presynapAc  terminal  2.  Be  released  when  neuron  is  sAmulated  3.  Cause  changes  in  membrane  potenAal  when  in  

synapAc  clem  4.  Include  a  mechanism  for  removal/uptake  5.  Drugs  should  induce  the  appropriate  response  

DON’T  WRITE  THESE  DOWN!!!  

SynapAc  transmission:  Chemical  1.  NeurotransmiWers  released  from  synapAc  

vesicles  at  acAve  zone  2.  Diffuse  across  clem    3.  Bind  to  receptor  sites  on  postsynapAc  cell  •  Driven  by  electrochemical  and  concentraAon  

gradients  

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SynapAc  transmission:  Chemical  

1.  AP  opens  voltage-‐gated  Ca+  channels  

2.  Ca+  rushes  in  (due  to  concentraAon  gradient)    à  synapAc  vesicles  release  Ach  into  synapAc  clem  

•  AP  arrives  at  presynapAc  terminal  

SynapAc  transmission:  Chemical  

3.  Ach  diffuses  through  clem  à  postsynapAc  membrane  

4.  Ligand-‐gated  Ach  receptor  channels  open  à    

5.  Na+  and  K+  rush  into  cell  

6.  Cell  is  excited  à  starts  new  AP    

•  AP  arrives  at  presynapAc  terminal  

SynapAc  transmission:  Chemical  

7.  Remainder  of  Ach  inhibited  by  enzyme    –  Enzyme  not  always  

necessary  8.  Re-‐uptake  back  

into  presynapAc  terminal  by  transporter  protein  

•  SynapAc  funcAons  won’t  proceed  while  Ach  present  in  synapAc  clem  

SynapAc  transmission:  Chemical  

•  AnimaAons  of  synapses  and  neurotransmiWer  release:  

Video  1  –  Synapse  Video  2  –  Synapse  Video  3  –  NeurotransmiWer  Video  4  –  NeurotransmiWer  release  

Psychiatric  condiAons  treated  with  neurotransmiWer    

•  Manipulate  synthesis  and/or  reuptake  of  specific  neurotranmsiWers  

•  EXAMPLE:  SelecAve  serotonin  reuptake  inhibitors  (SSRIs)    – Depression  treatment  

Less  serotonin    uptake    

More  serotonin  available  to  postsynapAc  neurons    

More  “happy  hormone”  moving  through  your  body